Patañjali (Devanāgarī) is the compiler of the Yoga Sutra, a major work containing aphorisms on the philosophical aspects of mind and consciousness, and also the author of a major commentary on Panini's Ashtadhyayi, although many scholars do not consider these two texts to have been written by the same individual. In recent decades the Yoga Sutra has become quite popular worldwide for the precepts regarding practice of Raja Yoga and the philosophical basis of the Yoga movement for health and harmonizing bodymind. "Yoga" in traditional Hinduism involves inner contemplation, a rigorous system of meditation practice, ethics, metaphysics, and devotion to the one common soul, God, or Brahman.
Desiring to teach yoga to the world, he is said to have fallen (pat-) from heaven into the open palms (-añjali) of a woman, hence the name Patañjali.
Patañjali as an incarnation
Patañjali is known to be an incarnation of Ādi S'esha who is the first ego-expansion of Vishnu, Sankarshana. Sankarshana, the manifestation of Vishnu His primeval energies and opulences, is part of the so-called catur vyūha, the fourfold manifestation of Vishnu. Thus may Patañjali be considered as the one incarnation of God defending the ego of yoga.
There are very many disputes about the background of Patanjali Maharishi but the works of his contemporary The Great Siddhar Thirumoolar is ample proof of the following detail.
Patanjali was born to Atri (First of the Saptha Rishis) and his wife Anusuya. He was one of the very important of the 18 siddhas.
Their very essence was they were masters of Ashtanga Yoga otherwise called as Raja Yoga or Kundalini Yoga or Tantrik yoga.
Anusiya had to go through a stern test of her chastity when the Thirumoorthies (Brahma, Vishnu, Siva) themselves came as Bhiksus and Asked her for a Nirvana Bhiksa. She passed their test by accepting themselves as her children and fed them in naked. She got the boon where all the 3 moorthies will be born to them. They were
1. SomaSkandan or Patanjali
They also had a daughter called Arundhati. She was married to Vashistar, one of the sapthaRishis.
It was here that Patanjali and his 7 other Yogic friends learnt the great Yoga from their Guru Nandhi deva as written in the thirumathiram by The great sage thirumoolar in Tantra 1.
Nandhi arulPetra Nadharai Naadinom
Nandhigal Nalvar Siva Yoga MaaMuni
Mandru thozhuda Patanjali Vyakramar
Endrivar Ennodu(Thirumoolar) Enmarumaam
By recieving Nandhi's grace we seeked the feet of Lord
The Four Nadhis , Siva Yoga Maamuni , Patanjali , Vyakramapadar and along with me (Thirumoolar)
Thus we were the Eight discliples.
Patanjali as Siddhar is also mentioned in Bogar MahaRishi's "Bhogar 7000"
It was my Grandfather who said, "Climb and see."
But it was Kalangi Nathar who gave me birth.
Patanjali,Viyagiramar,and Sivayogi Muni all so rightly said,
"Look! This is the path!"
They explained how to mount and go beyond.
And it was the Great Mother supreme who said,
"This is it!"
Having become calm... I perceived the accompanying experience.
Having experienced... I have composed 7000.
Bogar refers Thirumoolar as his Grandfather(GrandGuru) and kalangi as his father(Guru). Siddhars are masters of Kundalini yoga
Patanjali wrote the Great treatise of Yoga in Sanskrit whereas Thirumoolar wrote them as Thirumanthiram in Tamil. Thirumaloor attained jnana in South Kailash now called as thirumoorthy hills and he attained his MahaSamadhi in Rameshwaram.
He was a great dancer and is worshiped by the dancers of India as their patron saint. Doubt exists whether he as a dancer would be the same Patañjali as the one known as the author of the famous sūtras. Next to the famous works of the Yoga-sūtras and the commentary on Pānini's Sanskrit grammar a dispute as to identity lingers. His name is also associated with the Ashādhyāyī in a treatise called the Mahābhāsya, and also with many texts on ayurvedic medicine; but this claim is also not accepted as an established fact among scholars. Similarly disputed is whether the Sanskrit commentary of the Mahābhāsya is of the same Patañjali that established the Yoga Sutras, or perhaps another. There are contradictions in the philosophy of the sūtras and the Sanskrit commentary. So in all there might be three or four different Patañjalis adding to the fame of his name, a compilation of efforts all claiming the same identity.
The Yoga Sūtras
Some say that the Yoga Sūtras date from around 200 BC. Others date them to about AD 400. Patañjali has often been called the founder of Yoga because of this work, although in reality he is a more major figure. The Yoga Sūtras, as a treatise on Yoga, build on the Samkhya school and the Hindu scripture of the Bhagavad Gita (see also: Vyasa). Yoga, the science of uniting one's consciousness, is also found in the Puranas, the Vedas and the Upanishads. Still, this work is certainly a major work among the great Hindu scriptures and serves as the basis of the yoga-system known as Raja Yoga. Patañjali's Yoga is one of the six schools or darshanas of Hindu Philosophy. The sūtras give us the earliest reference to the popular term Ashtanga Yoga which translates literally as the eight limbs of yoga. They are yama, niyama, asana, pranayama, pratyahara, dharana, dhyana and samadhi.
The commentary on Sanskrit grammar: Mahābhāṣya
The Mahābhāsya ("great commentary") of Patañjali on the celebrated Ashādhyāyī of Pānini is one of the three most famous works in Sanskrit grammar. Patañjali's writings were extremely detailed especially regarding prakriyā or generative morphology, and the precise sequence, function and interpretation of Pānini's rules (sūtras). He also discussed the comments (vārttikas) of Kātyāyana, a scholar who lived between Pānini and Patañjali, sometimes supporting them and sometimes rejecting them. Kātyāyana's vārttikas are themselves often sūtra-like, and are only transmitted to us as embedded in Patañjali's discussion. It was the nineteenth-century scholar Franz Kielhorn who produced the first critical edition of the Mahābhāsya, and who developed sound philological criteria for distinguishing Kātyāyana's "voice" from Patañjali's. The main contribution of Patañjali lies in the fact that he revealed for later students a whole world of detailed, sophisticated discourse and debate surrounding Pānini's laconic sūtras.
Most historians of vyākarana do not consider the Patañjali who wrote the Mahābhāsya to be the same person as the author of the Yoga Sūtras. There are no parallel passages in the two works, no cross-references, and no common discussions. The two works show no awareness of each other, which is almost unknown in the writings of Sanskrit authors of multiple works. The traditions that a single Patañjali wrote on grammar, yoga, and medicine is first recorded in the comparatively late commentary on the Yoga Sūtras by Bhoja
Relevance of his contribution to the science of yoga
Patañjali defended in his yoga-treatise several ideas that are not mainstream of either Sankhya or Yoga. He, according the Iyengar adept, biographer and scholar Kofi Busia, acknowledges the ego not as a separate entity. The subtle body linga sarira he would not regard as permanent and he would deny it a direct control over external matters. This is not in accord with classical Sankhya and Yoga.
Evidently he was an original thinker, not just a compiler of the yoga wisdom known. Nevertheless he reinterpreted and clarified what others had said, undoing contradictions. Certainly, his genius brought together many lines of argument in the yoga philosophy, dating back in some respects to the Vedas and Upanishads. What was obscure he clarified and what was abstract he made practical, inspiring thus a long line of teachers and practitioners up to the present day in which his most renown defender is B.K.S. Iyengar. With some translators he seems to be a dry and technical propounder of the philosophy, but with others he is an empathic and humorous, witty friend and spiritual guide. For sure may he, with his practical summary of the essence of yoga, be regarded the greatest initiator into the science of uniting one's consciousness that is yoga.